Method for predicting long-term durability of resin composition for piping and olefinic polymer used for resin for piping

ABSTRACT

A method for evaluating long-term durability of a resin for piping is provided. Unlike the conventional FNCT evaluation method requiring a long period of time, the method disclosed herein is capable of predicting long-term durability of a resin for piping in a short time, by a simple calculation using a content of tie molecules, an entanglement molecular weight (M e ) and a content of ultrahigh molecular weight components. In addition, the olefinic polymer is configured to have a predetermined relationship in relation to the content of tie molecules, the entanglement molecular weight (M e ) and the content of ultrahigh molecular weight components, whereby the polymer of the present application can be used in the manufacture of a heating pipe requiring excellent long-term durability.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/KR2018/011478 filed on Sep. 28,2018 which claims priority from Korean Patent Application No.10-2017-0127803 filed on Sep. 29, 2017 and Korean Patent Application No.10-2018-0014323 filed on Feb. 6, 2018, with the Korean IntellectualProperty Office, the disclosures of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present application relates to a method for predicting long-termdurability of a resin for piping or a composition comprising the resin.The present application also relates to an olefinic polymer contained ina composition which can be used for forming a resin for piping.

BACKGROUND ART

Since plumbing pipes used in heating pipes are constructed insidebuildings, they should have excellent long-term durability so as toprevent water leakage due to cracks. Known methods for evaluatinglong-term durability of plumbing pipes are ISO 9080 and ISO 16770, andthe like. ISO 9080 is a method of estimating the pressure expected tocause cracks over 50 years by measuring the crack occurrence time overone year according to the temperature and pressure of water passingthrough a pipe and extrapolating this. Products with long-termdurability recognized by ISO 9080 have environmental stress crackresistance (ESCR) of about 2,000 hours or more, as measured at a stressof 4.0 MPa and a temperature of 80° C. by full notch creep test (FNCT)according to ISO 16770. That is, according to the above method, therelevant product has durability to the extent that the sample breaksafter 2,000 hours or more must elapse. However, there is a problem thatit takes at least 3 months to 1 year or more to perform the two methods.Therefore, a method capable of predicting long-term durability in aquick way is required, so that product development time can be shortenedby selecting a sample to be measured for long-term durability amongvarious samples in the product development stage.

Furthermore, it is considered that the long-term durability of the pipeused in the above application is affected by the characteristics of theresin used for forming the pipe. Therefore, there is a need for apolymer-related design standard that can ensure long-term durability ofthe pipe.

DISCLOSURE Technical Problem

It is one object of the present application to provide a method forpredicting long-term durability of a resin composition for piping in ashort time.

It is another object of the present application to provide a method forcomparatively evaluating long-term durability for a plurality of resincompositions for piping.

It is another object of the present application to provide a polymerwhich can be used for manufacturing a heater-plumbing pipe havingexcellent long-term durability.

It is another object of the present application to provide a resincomposition for heater-piping having excellent environmental stresscrack resistance.

The above objects and other objects of the present application can beall solved by the present application which is described in detailbelow.

Technical Solution

In one example concerning the present application, the presentapplication relates to a method for predicting or evaluating long-termdurability of a resin composition for piping.

In the present application, the sample to be predicted or evaluated maybe a resin or a resin composition containing other components.Furthermore, in the present application, the resin (composition) forpiping may mean a resin (composition) used in a pipe forming a movingpath of a fluid or the like, and may mainly mean a resin (composition)for heater-piping.

The long-term durability prediction method of the present applicationuses a tie molecule, an entanglement molecular weight (Me) and amass-average molecular weight (Mw) as factors for predicting long-termdurability.

In the present application, the tie molecule, which is one of thefactors used for predicting long-term durability, means a polymermolecule connecting crystals of an amorphous polymer resin. In theamorphous polymer molecule, crystals of lamellar structures are formedby chain folding below a crystallization temperature. At this time, if apolymer structure capable of forming a defect in the crystal structure,for example, an α-olefin or an LCB (long chain branch), is present, therelevant moiety does not form crystals and remains amorphous. On theother hand, the lamellar structures can be formed in the moiety where noα-olefin or LCB structure is present, so that one polymer chain can formcrystalline-amorphous-crystalline structures. In such a structure, theamorphous moiety serves to connect the crystal to the crystal, which isreferred to as a tie molecule. As the polymer molecule has a highmolecular weight and thus the length of the polymer chain is longer, theprobability that the tie molecules will be produced increases. Asdescribed above, the higher the content of the tie molecules is, thestronger the connection between the crystal structures is, and thus itis considered that crack generation and propagation become difficult.Taking this point into consideration, in the present application, thecontent of tie molecules is used as one factor for predicting long-termdurability. At this time, the content of tie molecules means a % ratio,that is, a wt %, of the polymer molecules forming the tie moleculesbased on the weight 100 of the entire polymer molecule contained in theresin composition. The content of tie molecules can be determined asdescribed below.

When one polymer chain is tangled with the surrounding polymers oritself to form an entanglement point functioning as a physicalcrosslink, the entanglement molecular weight (M_(e)), which is anotherfactor used in the present application method, means an averagemolecular weight between such entanglement points. As the polymermolecule has a high molecular weight and thus the length of the polymerchain is longer, the probability that entanglement points will begenerated increases, so that the entanglement molecular weightdecreases. The smaller the entanglement molecular weight, the greaterthe entanglement degree of the polymer, and thus it is considered thatthe resistance to external force increases. Taking this point intoconsideration, in the present application, the entanglement molecularweight is used as one of factors of long-term durability prediction. Theentanglement molecular weight can be measured as described below.

Another of the factors used in the long-term durability prediction ofthe present application is the content of an ultrahigh molecular weightcomponent. At this time, the ultrahigh molecular weight means a casewhere the mass average molecular weight (Mw) is 1,000,000 or more, andthe content of the ultrahigh molecular weight component means a % ratio,that is, a wt %, of the polymer having a mass average molecular weightof 1,000,000 or more based on the weight 100 of the entire polymercontained in the resin composition. The higher the content of theultrahigh molecular weight component, the larger the number of polymermolecules having a longer polymer chain length, and thus it isconsidered that the entanglement of the polymer chain or the content oftie molecules increases. Taking this point into consideration, in thepresent application, the content of the ultrahigh molecular weightcomponent is used as one factor for predicting the long-term durability.The content of the ultrahigh molecular weight component can be measuredas described below.

According to the present application in which the above factors are usedfor the long-term durability measurement of a resin composition as asample, the long-term durability of the resin composition can bepredicted or evaluated in a short time even if a small amount of asample is used.

Specifically, the method according to the present application canpredict or evaluate the long-term durability of a resin composition as asample by using the following equation.Long-term durability predicted value of resincomposition=a×(X)^(b)×(Y)^(c)×(Z)^(d)  [Equation]

In Equation above, a=386,600, b=4.166, c=−1.831, and d=1.769.Furthermore, X, Y and Z are values relating to molecular characteristicsthat can be measured in a resin composition as a sample, respectively.Specifically, X means a content (wt %) of tie molecules, Y means anentanglement molecular weight (g/mol), and Z means a content (wt %) of acomponent having a mass average molecular weight (Mw) of 1,000,000 ormore. At this time, X, Y and Z are used as dimensionless constantsexcluding the units.

The inventors of the present application have confirmed that thepredicted value concerning the long-term durability calculated accordingto Equation above is very similar to the environmental stress crackresistance evaluation result actually measured by the full notch creeptest (FNCT) according to ISO 16770 at 4.0 MPa and 80° C. Therefore, if apredicted value of the long-term durability of a resin composition as asample is calculated according to the present application, the long-termdurability of a resin composition for piping can be predicted orevaluated in a short time by only simple calculation without performingthe durability evaluation over a long period of time such as ISO 9080 orISO 16770.

In the present application, the predicted value calculation of long-termdurability can be made for a plurality of samples. In this case, it canbe determined that the long-term durability of the sample having thelargest calculated value is the most excellent.

In the present application, a sample to be predicted or evaluated forlong-term durability, that is, a resin composition may comprise ahomopolymer formed from one monomer component and/or a copolymer formedfrom a plurality of different monomer components. Then, the resincomposition may also comprise one or more homopolymers or copolymers.

In one example, the resin composition as the sample may comprise apolyolefin. The kind of the polyolefin is not particularly limited. Forexample, the polyolefin may be a polymer formed from ethylene, butylene,propylene, and/or α-olefinic monomers. The kind of the α-olefinicmonomer is not particularly limited. For example, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene or 1-eicosene, andthe like can be used, without being particularly limited thereto.

In one example concerning the present application, the presentapplication relates to an olefinic polymer. The polymer can be used in apipe forming a moving path of a fluid or the like, and can be mainlyused for forming a heating pipe. Since the polymer satisfiespredetermined conditions and/or configurations to be described below, ithas excellent long-term durability which can be confirmed, for example,through evaluation of environmental stress crack resistance.

In the present application, as design factors of the olefinic polymer, acontent of tie molecules, an entanglement molecular weight (Me) and acontent of an ultrahigh molecular weight component can be used.

In the present application, the tie molecule, which is one of the designfactors of a polymer, means a polymer molecule connecting crystals of anamorphous polymer resin. In the amorphous polymer molecule, crystals oflamellar structures are formed by chain folding below a crystallizationtemperature. At this time, if a polymer structure capable of forming adefect in the crystal structure, for example, an α-olefin or an LCB(long chain branch), is present, the relevant moiety does not formcrystals and remains amorphous. On the other hand, the lamellarstructures can be formed in the moiety where no α-olefin or LCBstructure is present, so that one polymer chain can formcrystalline-amorphous-crystalline structures. In such a structure, theamorphous moiety serves to connect the crystal to the crystal, which isreferred to as a tie molecule. As the polymer molecule has a highmolecular weight and thus the length of the polymer chain is longer, theprobability that the tie molecules will be produced increases. Asdescribed above, the higher the content of the tie molecules is, thestronger the connection between the crystal structures is, and thus itis considered that crack generation and propagation become difficult.Taking this into consideration, in the present application, the contentof tie molecules is used as one factor of the polymer design used forthe above application. At this time, the content of tie molecules meansa % ratio, that is, a wt %, of the (polymer) component forming the tiemolecules based on the weight 100 of the entire polymer moleculecontained in the resin composition. The content of tie molecules can bedetermined as described below.

When one polymer chain is tangled with the surrounding polymers oritself to form an entanglement point functioning as a physicalcrosslink, the entanglement molecular weight (M_(e)), which is anotherfactor used in the present application, means an average molecularweight between such entanglement points. As the polymer molecule has ahigh molecular weight and thus the length of the polymer chain islonger, the probability that entanglement points will be generatedincreases, so that the entanglement molecular weight decreases. Thesmaller the entanglement molecular weight, the greater the entanglementdegree of the polymer, and thus it is considered that the resistance toexternal force increases. Taking this point into consideration, thepresent application uses the entanglement molecular weight as one factorin the polymer design used for the above application. The entanglementmolecular weight can be measured as described below.

Another of the factors used in the present application is the content ofan ultrahigh molecular weight component. At this time, the ultrahighmolecular weight means a case where the mass average molecular weight(Mw) is 1,000,000 or more, and the content of the ultrahigh molecularweight component means a % ratio, that is, a wt %, of the (polymer)component having a mass average molecular weight of 1,000,000 or morebased on the weight 100 of the entire polymer. The higher the content ofthe ultrahigh molecular weight component, the larger the number ofpolymer molecules having a longer polymer chain length, and thus it isconsidered that the entanglement of the polymer chain or the content oftie molecules increases. Taking this point into consideration, thepresent application uses the content of the ultrahigh molecular weightcomponent as one factor of the polymer design used for the aboveapplication. The content of the ultrahigh molecular weight component canbe measured as described below.

The inventors of the present application have confirmed that when theolefinic polymer is designed to satisfy a predetermined relationshipwith regard to such factors, it is possible to provide a resin forheater-piping having excellent long-term durability. Specifically, theolefinic polymer of the present application may be an olefinic polymersatisfying at least two conditions of the following conditions [A] to[C].

[A] A content of tie molecules is 10 wt % or more

[B] An entanglement molecular weight (Me) is 17,000 g/mol or less

[C] A content of a component having a mass average molecular weight (Mw)of 1,000,000 or more is 2.5 wt % or more

When at least two conditions of [A] to [C] are satisfied, it is possibleto show excellent long-term durability characteristics in theenvironmental stress crack resistance (ESCR) evaluation measured by thefull notch creep test (FNCT) according to ISO 16770 at 4.0 MPa and 80°C. For example, time characteristics to be described below can besatisfied.

In one example, the polymer may further satisfy the condition that thecontent of tie molecules is 30 wt % or less, 25 wt % or less, or 20 wt %or less with regard to the above condition [A]. Upon designing thepolymer for the predetermined application, in consideration of thesignificance that the content of tie molecules as described above has,an increase in the content can be considered. To increase the content oftie molecules, the density of the polymer should be lowered or thecontent of the higher molecular weight component should be increased.However, if the density decreases, the pressure-resistant performance ofthe final pipe product declines, and if the content of the polymercomponent increases, the viscosity increases, whereby there is a problemthat the processability deteriorates, so that it is preferable tocontrol the content of tie molecules in the above content range.

In another example, the polymer may further satisfy the condition thatthe entanglement molecular weight (Me) is 1000 g/mol or more, 2000 g/molor more, 3000 g/mol or more, 4000 g/mol or more, or 5000 g/mol or morewith regard to the above condition [B]. Upon designing the polymer forthe predetermined application, in consideration of the significance thatthe content of the entanglement molecular weight as described above has,a decrease in the molecular weight can be considered. However, when theentanglement molecular weight is too low, the content of the highmolecular weight component becomes high, so that the processability islowered. In addition, since breakage easily occurs in the stretchingprocess for adjusting dimensions and the like such as a diameter or athickness after extruding the produced pipe, there is also a need tostretch it at a low speed, so that there is a problem that productivityis lowered. Therefore, it is preferable to have molecular weight morethan the said range.

In another example, the polymer may further satisfy the condition thatthe content of the component having a mass average molecular weight (Mw)of 1,000,000 or more is 20 wt % or less, 15 wt % or less, or 10 wt % orless with regard to the above condition [C]. If the content of theultrahigh molecular weight component exceeds the above range, theprocessability may be deteriorated.

In another example, the polymer may satisfy all of the conditions [A] to[C]. When all the three conditions are satisfied, more excellentlong-term durability can be ensured.

The kind of the monomer for forming the olefinic polymer is notparticularly limited. For example, the olefinic polymer may be formedfrom a monomer mixture comprising ethylene, butylene, propylene, orα-olefinic monomers. That is, the polymer of the present application maybe one prepared by polymerizing one or more monomers of the abovemonomers. At this time, the kind of the α-olefinic monomer is notparticularly limited. For example, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene or 1-eicosene, andthe like can be used, without being particularly limited thereto.

In one example, the monomer mixture may comprise two or more monomersselected from ethylene, butylene, propylene, and α-olefinic monomers. Atthis time, the two or more monomers contained in the monomer mixture maybe different from each other, where the kind of the α-olefinic monomeris the same as those listed above.

In one example, the olefinic polymer may comprise ethylene as a maincomponent. In the present application, in relation to the components ofthe polymer, the main component monomer may means a case where thecontent of the main component monomer exceeds 50 wt % based on thecontent 100 of the total monomers used for forming the polymer. Theupper limit of the main component monomer content is not particularlylimited, but may be, for example, 95 wt % or less, 90 wt % or less, 85wt % or less, 80 wt % or less, 75 wt % or less, or 70 wt % or less. Inthis case, the monomer mixture may comprise one or more monomersselected from butylene, propylene, and α-olefinic monomers as acopolymerizable monomer, in addition to ethylene as the main component.The copolymerizable monomer may be used in the monomer mixture as muchas the remaining content other than the content of ethylene as the mainmonomer.

In one example, 1-butene (1-C4) may be used as the copolymerizingmonomer for forming the olefinic polymer. Specifically, a monomer havinga short length, for example, 1-butene may be used due to influences ofthe characteristics of the polymerization equipment or the supply anddemand of raw materials, and the like. However, in such a case, thelong-term durability may be lowered as compared with a product producedusing a relatively long copolymerizing monomer, for example, 1-hexene(1-C6) or 1-octene (1-C8), and the like. However, when theabove-described conditions of the present application are satisfied,superior long-term durability can be ensured even when a copolymerizingmonomer having a relatively short length such as 1-butene is used. Thecontent of 1-butene to be used is not particularly limited, but may beused so as to satisfy a range of about 7.0 to 10.1/1,000 C as a resultof FT-IR analysis.

The polymer satisfying the above conditions and configuration may haveenvironmental stress cracking resistance (ESCR) of 1500 hours or moremeasured by the full notch creep test (FNCT) according to ISO 16770 at4.0 MPa and 80° C. More preferably, the polymer may have environmentalstress cracking resistance (ESCR) of 2000 hours to 8000 hours measuredby the full notch creep test (FNCT) according to the same conditions andmethod.

Advantageous Effects

According to one example of the present application, a method capable ofpredicting long-term durability of a resin for piping in a short timeusing a small amount of a sample can be provided. Also, according to thepresent application, since the long-term durability of the resin forpiping can be evaluated in a short time, a polymer structure havingexcellent long-term durability can be usefully designed and a samplethat is worth actually measuring long-term durability can be selected ina short time, so that the efficiency of the product development stagecan be improved and the development time can be shortened. In addition,according to the present application, an olefinic polymer structurehaving excellent long-term durability can be usefully designed, and aplumbing pipe having excellent long-term durability can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIGURE is a graph showing the correlation between FNCT measured valuesof the resin used in a Preparation Example and FNCT predicted valuescalculated for each resin of the present application examplescorresponding to the Preparation Example.

BEST MODE

Hereinafter, the present application will be described in detail throughexamples. However, the protection scope of the present application isnot limited by the following examples.

Experimental Example 1: Experimental Example on Long-Term DurabilityPrediction

The relevant physical properties and the like measured in the followingexperimental examples were measured according to the following methods.

Measuring Method

-   -   FNCT (full notch creep test) measured value: For the resins of        Preparation Examples 1 to 15 prepared below, a full notch creep        test was performed according to ISO 16770 at a stress of 4.0 MPa        and a temperature of 80° C. Specifically, a specimen for        performing the FNCT was a rectangular parallelepiped having a        size of 10×10×100 mm, which was obtained by milling a plate        having a thickness of 15 mm. Then, notches having a depth of 1.5        mm were formed on four sides of the specimen, a stress of 4.0        MPa was applied to the specimen in a 10% Igepal solution at 80°        C., and then the time taken until the specimen was broken was        measured. Based on the measured time, the properties of the        resins were qualitatively classified according to the following        criteria.

<Qualitative Classification of FNCT Measured Values>

-   -   above 2,000 hours: excellent    -   1,500 hours to less than 2,000 hours: somewhat excellent    -   1,000 hours to less than 1,500 hours: normal    -   400 hours to less than 1,000 hours: somewhat poor    -   less than 400 hours: poor    -   Content of tie molecules: The molecular weight distribution,        melting point (Tm) and mass fraction crystallinity were        calculated in the following methods, and the content of tie        molecules was calculated from these values.

Molecular weight distribution: 10 mg of a sample to be measured wasdissolved in 1,2,4-trichlorobenzene containing 0.0125% of BHT at 160° C.for 10 hours and pretreated using PL-SP260 from Agilent, and a GPC curvewas obtained using PL-GPC220 as GPC (gel permeation chromatography) forhigh temperature.

Melting point and mass fraction crystallinity: 5 mg of a sample to bemeasured was placed on an Al pan, covered with an Al lid, and thenpunched and sealed, and it was heated from 50° C. to 190° C. at 10°C./min using DSC Q20 from TA (Cycle 1), and cooled to 50° C. at 10°C./min after isothermal treatment at 190° C. for 5 minutes, and thenheated again to 190° C. at 10° C./min after isothermal treatment at 50°C. for 5 minutes (Cycle 2). The melting point and mass fractioncrystallinity were calculated from the temperature (Tm) and area (ΔH) ofthe DSC curve peak in the range of 60° C. to 140° C. in Cycle 2.

Tm: temperature of DSC curve peak

Mass fraction crystallinity: ΔH/293.6×100 (293.6: ΔH at 100% crystal)

Content calculation of tie molecules: The content of tie molecules wascalculated from the area of the tie molecule distribution graph in whichthe x-axis was the molecular weight M and the y-axis was represented byn·P·dM. The corresponding graph is calculated from the GPC curve and DSCmeasurement results. With regard to the y-axis, n is the number of thepolymer molecules having a molecular weight of M, which can be obtainedas (dw/d log Mw)/M from the data of the GPC curve in which the x-axis islog Mw and the y-axis is dw/d log Mw. In addition, the P is aprobability that the polymer molecules having a molecular weight of Mform tie molecules, which can be calculated from the following equations1 to 3, and the dM is an interval between the x-axis data (molecularweight M) of the GPC curve.

$\begin{matrix}{P = {\frac{1}{3}\frac{\int_{{2\; l_{c}} + l_{c}}^{\infty}{r^{2}{\exp( {{- b^{2}}r^{2}} )}{dr}}}{\int_{0}^{\infty}{r^{2}{\exp( {{- b^{2}}r^{2}} )}{dr}}}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In Equation 1 above, r is an end-to-end distance of a random coil, b² is3/2r², le is a crystal thickness, which is obtained from Equation 2below, and l_(a) is an amorphous thickness, which is obtained fromEquation 3 below.

$\begin{matrix}{T_{m} = {T_{m}^{o}( {1 - \frac{2\;\sigma_{e}}{\Delta\; h_{m}l_{c}}} )}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

In Equation 2 above, T°_(m) is 415K, σ_(e) is 60.9×10⁻³ J/m², and Δh_(m)is 2.88×10³ J/m³.l _(a)=ρ_(c) l _(c)(1−ω^(c))/ρ_(a)ω^(c)  [Equation 3]

In Equation 3 above, pc is a crystal density, which is 1,000 kg/m³,ρ_(a) is a density of amorphous phase, which is 852 kg/m³, ω^(c) isweight fraction crystallinity, which is confirmed from DSC results.

-   -   Calculation of entanglement molecular weight (Me): Using a        rotary rheometer, a storage elastic modulus and a loss elastic        modulus of each sample were measured under conditions of a        temperature of 150° C. to 230° C., an angular frequency of 0.05        to 500 rad/s and a strain of 0.5%, and from the plateau elastic        modulus (GN0) thus obtained, the entanglement molecular weight        was calculated according to Theoretical Equation below. However,        in Theoretical Equation below, p means a density (kg/m³), R is        the gas constant (8.314 Pa·m³/mol·K) and T is the absolute        temperature (K).        M _(e)=(ρRT)/G _(N) ⁰  [Theoretical Equation]    -   Content measurement and calculation of ultrahigh molecular        weight component: In the molecular weight distribution analysis        result of the sample, the area ratio (%) of the portion having a        molecular weight of 1,000,000 or more relative to the total area        was calculated.    -   Long-term durability predicted value: The predicted value of        long-term durability was calculated by substituting the values        obtained from the above into the following equation.        Long-term durability predicted value of resin        composition=a×(X)^(b)×(Y)^(c)×(Z)^(d)  [Equation]

However, in Equation above, a=386,600, b=4.166, c=−1.831, and d=1.769,X, Y and Z mean, in a resin composition as a sample, a content (wt %) oftie molecules, an entanglement molecular weight (g/mol) and a content(wt %) of a component having a mass average molecular weight (Mw) of1,000,000 or more, respectively. At this time, in Equation above, X, Yand Z are used as dimensionless constants excluding the units.

Based on the predicted value calculated from Equation above, thecharacteristics of the resin were classified qualitatively by thefollowing criteria.

<Qualitative Classification of Predicted Values>

-   -   above 2,000: excellent    -   1,500 to less than 2,000: somewhat excellent    -   1,000 to less than 1,500: normal    -   400 to 1,000: somewhat poor    -   less than 400: poor

PREPARATION EXAMPLES

A resin as a target for long-term durability measurement was prepared asfollows. Then, the time was measured according to the FNCT (full notchcreep test). The results are shown in Table 1.

Preparation Example 1: In a hexane slurry CSTR process, the resin waspolymerized while supplying ethylene, hydrogen and 1-butene at apredetermined input rate using a metallocene catalyst. The preparedresin had a density of 0.9396 g/cm³ as measured according to ASTM D 1505and an MI (melt index) of 0.26 as measured under conditions of 190° C.and 2.16 kg/10 min according to ASTM D 1238.

Preparation Example 2: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9392g/cm³ and the MI was 0.34.

Preparation Example 3: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9358g/cm³ and the MI was 0.75.

Preparation Example 4: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9359g/cm³ and the MI was 0.47.

Preparation Example 5: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9363g/cm³ and the MI was 0.27.

Preparation Example 6: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9396g/cm³ and the MI was 0.32.

Preparation Example 7: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9365g/cm³ and the MI was 0.60.

Preparation Example 8: A resin was prepared in the same manner as inPreparation Example 3, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9367g/cm³ and the MI was 0.47.

Preparation Example 9: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9369g/cm³ and the MI was 0.38.

Preparation Example 10: A resin was prepared in the same manner as inPreparation Example 1, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9364g/cm³ and the MI was 0.48.

Preparation Example 11: A resin was prepared in the same manner as inPreparation Example 1, except that the density was 0.9362 g/cm³ and theMI measured under the same conditions was 0.43.

Preparation Example 12: A resin was prepared in the same manner as inPreparation Example 1 except that the density was 0.9363 g/cm³ and theMI measured under the same conditions was 0.26.

Preparation Example 13: A resin was prepared in the same manner as inPreparation Example 1, except that the density was 0.9362 g/cm³ and theMI measured under the same conditions was 0.44.

Preparation Example 14: A resin was prepared in the same manner as inPreparation Example 1, except that the density was 0.9357 g/cm³ and theMI measured under the same conditions was 0.25.

Preparation Example 15: A resin was prepared in the same manner as inPreparation Example 1, except that the density was 0.9363 g/cm³ and theMI measured under the same conditions was 0.39.

Examples Example 1

For the sample prepared in Preparation Example 1, the content of tiemolecules, the entanglement molecular weight, and the content of theultrahigh molecular weight component were measured according to theabove methods, and the predicted value concerning long-term durabilitywas calculated by substituting them into Equation according to thepresent application. The result is as shown in Table 2.

Examples 2 to 15

The contents of tie molecules, the entanglement molecular weights andthe contents of the ultrahigh molecular weight components were measuredand the predicted values concerning the durability were calculated, inthe same manner as in Example 1, except that in Examples 2 to 15, theresins prepared in accordance with Preparation Examples 2 to 15 in thisorder were used, respectively.

TABLE 1 Preparation FNCT measured value Example (hour) Remark 1 2310Excellent 2 376 Poor 3 59 Poor 4 206 Poor 5 2000 Excellent 6 1710Somewhat excellent 7 244 Poor 8 285 Poor 9 416 Somewhat poor 10 114 Poor11 138 Poor 12 1537 Somewhat excellent 13 155 Poor 14 1354 Normal 15 168Poor

TABLE 2 Content of ultrahigh Content molecular Long-term of tie weightdurability molecules Me component predicted Example (%) (g/mol) (%)value Remark 1 12.4 13900 2.8 2226 Excellent 2 10.6 19500 2.4 474Somewhat poor 3 9.6 36700 2.0 71 Poor 4 11.2 25600 2.6 418 Somewhat poor5 11.3 15800 3.7 1958 Somewhat excellent 6 8.2 11700 5.2 1629 Somewhatexcellent 7 9.5 35900 1.2 29 Poor 8 9.8 28200 1.2 51 Poor 9 9.5 233001.6 106 Poor 10 10.2 25100 1.3 86 Poor 11 11.0 23800 1.8 231 Poor 1211.2 12500 2.8 1770 Somewhat excellent 13 10.6 25300 1.6 144 Poor 1411.9 15100 2.3 1138 Normal 15 11.8 22800 1.4 215 Poor

Comparing the FNCT measured values in Table 1 with the dimensionlesscalculated values in Table 2, it can be seen that their values are verysimilar. Then, it can be confirmed that the measured values and thecalculated values can be evaluated very similarly even in thequalitative classification. Actually, it is also confirmed in FIGUREthat the X-axis and the Y-axis have a strong linear correlation. Thatis, the durability prediction method of the present application canreplace the conventional FNCT measurement method. In other words, themethod according to the present application can evaluate the durabilityof the resin (composition) for piping in a short time only by measuringthe molecular weight and the like, even without going through a testingperiod of several months or more.

Experimental Example 2: Confirmation of Suitability as Polymer forHeater-Piping

The relevant physical properties and the like measured in the followingexperimental examples were measured according to the following methods.

Measuring Method

-   -   FNCT (full notch creep test) measured value: For the polymers of        Preparation Examples 1 to 14 prepared below, a full notch creep        test was performed according to ISO 16770 at a stress of 4.0 MPa        and a temperature of 80° C. Specifically, a specimen for        performing the FNCT was a rectangular parallelepiped having a        size of 10×10×100 mm, which was obtained by milling a plate        having a thickness of 15 mm. Then, notches having a depth of 1.5        mm were formed on four sides of the specimen, a stress of 4.0        MPa was applied to the specimen in a 10% Igepal solution at 80°        C., and then the time taken until the specimen was broken was        measured. Based on the measured time, the properties of the        resins were qualitatively classified according to the following        criteria.

<Qualitative Classification of FNCT Measured Values>

-   -   above 2,000 hours: excellent    -   1,500 hours to less than 2,000 hours: somewhat excellent    -   1,000 hours to less than 1,500 hours: normal    -   400 hours to less than 1,000 hours: somewhat poor    -   less than 400 hours: poor    -   Content of tie molecules: The molecular weight distribution,        melting point (Tm) and mass fraction crystallinity were        calculated in the following methods, and the content of tie        molecules was calculated from these values.    -   Molecular weight distribution: 10 mg of a sample to be measured        was dissolved in 1,2,4-trichlorobenzene containing 0.0125% of        BHT at 160° C. for 10 hours and pretreated using PL-SP260 from        Agilent, and a GPC curve was obtained using PL-GPC220 as GPC        (gel permeation chromatography) for high temperature.    -   Melting point and mass fraction crystallinity: 5 mg of a sample        to be measured was placed on an Al pan, covered with an Al lid,        and then punched and sealed, and it was heated from 50° C. to        190° C. at 10° C./min using DSC Q20 from TA (Cycle 1), and        cooled to 50° C. at 10° C./min after isothermal treatment at        190° C. for 5 minutes, and then heated again to 190° C. at 10°        C./min after isothermal treatment at 50° C. for 5 minutes (Cycle        2). The melting point and mass fraction crystallinity were        calculated from the temperature (Tm) and area (ΔH) of the DSC        curve peak in the range of 60° C. to 140° C. in Cycle 2.

Tm: temperature of DSC curve peak

Mass fraction crystallinity: ΔH/293.6×100 (293.6: ΔH at 100% crystal)

-   -   Content calculation of tie molecules: The content of tie        molecules was calculated from the area of the tie molecule        distribution graph in which the x-axis was the molecular weight        M and the y-axis was represented by n·P·dM. The corresponding        graph is calculated from the GPC curve and DSC measurement        results. With regard to the y-axis, n is the number of the        polymer molecules having a molecular weight of M, which can be        obtained as (dw/d log Mw)/M from the data of the GPC curve in        which the x-axis is log Mw and the y-axis is dw/d log Mw. In        addition, the P is a probability that the polymer molecules        having a molecular weight of M form tie molecules, which can be        calculated from the following equations 1 to 3, and the dM is an        interval between the x-axis data (molecular weight M) of the GPC        curve.

$\begin{matrix}{P = {\frac{1}{3}\frac{\int_{{2\; l_{c}} + l_{c}}^{\infty}{r^{2}{\exp( {{- b^{2}}r^{2}} )}{dr}}}{\int_{0}^{\infty}{r^{2}{\exp( {{- b^{2}}r^{2}} )}{dr}}}}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In Equation 1 above, r is an end-to-end distance of a random coil, b² is3/2r², l_(c) is a crystal thickness, which is obtained from Equation 2below, and l_(a) is an amorphous thickness, which is obtained fromEquation 3 below.

$\begin{matrix}{T_{m} = {T_{m}^{o}( {1 - \frac{2\;\sigma_{e}}{\Delta\; h_{m}l_{c}}} )}} & \lbrack {{Equation}\mspace{14mu} 2} \rbrack\end{matrix}$

In Equation 2 above, T°_(m) is 415K, ae is 60.9×10⁻³ J/m², and Δh_(m) is2.88×10³ J/m³.l _(a)=ρ_(c) l _(c)(1−ω^(c))/ρ_(a)ω^(c)  [Equation 3]

In Equation 3 above, ρ_(c) is a crystal density, which is 1,000 kg/m³,ρ_(a) is a density of amorphous phase, which is 852 kg/m³, ω^(c) isweight fraction crystallinity, which is confirmed from DSC results.

-   -   Calculation of entanglement molecular weight (M_(e)): Using a        rotary rheometer, a storage elastic modulus and a loss elastic        modulus of each sample were measured under conditions of a        temperature of 150° C. to 230° C., an angular frequency of 0.05        to 500 rad/s and a strain of 0.5%, and from the plateau elastic        modulus (GN0) thus obtained, the entanglement molecular weight        was calculated according to Theoretical Equation below. However,        in Theoretical Equation below, p means a density (kg/m³), R is        the gas constant (8.314 Pa·m³/mol·K) and T is the absolute        temperature (K).        M _(e)=(ρRT)/G _(N) ⁰  [Theoretical Equation]    -   Content measurement and calculation of ultrahigh molecular        weight component: In the molecular weight distribution analysis        result of the sample, the area ratio (%) of the portion having a        molecular weight of 1,000,000 or more relative to the total area        was calculated.

Preparation Examples

Preparation Example 1: In a hexane slurry CSTR process, the resin waspolymerized while supplying ethylene, hydrogen and 1-butene at apredetermined input rate using a metallocene catalyst capable ofproducing a bimodal molecular weight distribution. The prepared resinhad a density of 0.9365 g/cm³ as measured according to ASTM D 1505 andan MI (melt index) of 0.02 as measured under conditions of 190° C. and2.16 kg/10 min according to ASTM D 1238.

Preparation Example 2: A resin was prepared in the same manner as inPreparation Example 1, except that a metallocene catalyst of a differentkind from that of Preparation Example 1 was used. The density of theprepared resin was 0.9396 g/cm³ and the MI was 0.26.

Preparation Example 3: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9392g/cm³ and the MI was 0.34.

Preparation Example 4: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9358g/cm³ and the MI was 0.75.

Preparation Example 5: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9363g/cm³ and the MI was 0.27.

Preparation Example 6: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9396g/cm³ and the MI was 0.32.

Preparation Example 7: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9365g/cm³ and the MI was 0.60.

Preparation Example 8: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9367g/cm³ and the MI was 0.47.

Preparation Example 9: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9369g/cm³ and the MI was 0.38.

Preparation Example 10: A resin was prepared in the same manner as inPreparation Example 2, except that the input rate of the raw materialswas controlled differently. The density of the prepared resin was 0.9364g/cm³ and the MI was 0.48.

Preparation Example 11: A resin was prepared in the same manner as inPreparation Example 2, except that the density was 0.9362 g/cm³ and theMI measured under the same conditions was 0.43.

Preparation Example 12: A resin was prepared in the same manner as inPreparation Example 2, except that the density was 0.9363 g/cm³ and theMI measured under the same conditions was 0.26.

Preparation Example 13: A resin was prepared in the same manner as inPreparation Example 2, except that the density was 0.9362 g/cm³ and theMI measured under the same conditions was 0.44.

Preparation Example 14: A resin was prepared in the same manner as inPreparation Example 2, except that the density was 0.9363 g/cm³ and theMI measured under the same conditions was 0.39.

Examples

For the sample prepared in each of Preparation Examples, the content oftie molecules, the entanglement molecular weight and the content of theultrahigh molecular weight component were measured according to theabove methods. Alternatively, for the sample prepared in each ofPreparation Examples above, the environmental stress crack resistancemeasured by FNCT was measured. The results are as shown in Table 3.

TABLE 3 Content of ultrahigh Content molecular of tie weight moleculesMe component FNCT Example (%) (g/mol) (%) (hour) Remark 1 12.2 1400 10.26500 Excellent 2 12.4 13900 2.8 2310 Excellent 3 10.6 19500 2.4 376 Poor4 9.6 36700 2.0 59 Poor 5 11.3 15800 3.7 2000 Excellent 6 8.2 11700 5.21710 Somewhat excellent 7 9.5 35900 1.2 244 Poor 8 9.8 28200 1.2 285Poor 9 9.5 23300 1.6 416 Somewhat poor 10 10.2 25100 1.3 114 Poor 1111.0 23800 1.8 138 Poor 12 11.2 12500 2.8 1534 Somewhat excellent 1310.6 25300 1.6 155 Poor 14 11.8 22800 1.4 168 Poor

Referring to Table 3 above, it can be seen that if at least twoconditions of the conditions defined in the present application aresatisfied, a polymer for heater-piping having excellent long-termdurability can be designed.

The invention claimed is:
 1. A method for predicting long-termdurability of a resin composition for piping comprising: collecting dataof the resin composition, the data comprising a content (wt %) of tiemolecules, an entanglement molecular weight (M_(e)), and a content (wt%) of a component having a mass average molecular weight (M_(w)) of1,000,000 or more; and using Equation below to determine a value oflong-term durability of the resin composition:Long-term durability predicted value of resincomposition=a×(X)^(b)×(Y)^(c)×(Z)^(d)  [Equation] wherein, a=386,600,b=4.166, c=−1.831, and d=1.769, X, Y and Z represent, in the resincomposition, the content (wt %) of tie molecules, the entanglementmolecular weight (M_(e)), and the content (wt %) of the component havingthe mass average molecular weight (M_(w)) of 1,000,000 or more,respectively, where X, Y and Z are used as dimensionless constantsexcluding their respective units.
 2. The method according to claim 1,further comprising: determining the value of long-term durability bycalculating through the Equation to evaluate a long-term durability ofthe resin composition.
 3. The method according to claim 1, furthercomprising: comparing the value of long-term durability determined bycalculating through the Equation for each resin composition of aplurality of resin compositions.
 4. The method according to claim 1,wherein the resin composition comprises a polyolefin resin.
 5. Themethod according to claim 4, wherein the polyolefin resin is a polymerof ethylene, butene, propylene or α-olefin monomers.
 6. The method ofclaim 1, wherein the long-term durability is excellent when the longterm durability predicted value of the resin composition calculated fromthe Equation is greater than
 2000. 7. The method of claim 1, wherein thelong term durability predicted value of the resin composition calculatedfrom the Equation has a linear correlation with a value measured from afull notch creep test (FNCT).